Reading Weight from Machine Using PORT

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Hi All,

I am using this code to read weight from weighing machine.

C#

_serialPort = new SerialPort("COM2", 9600, Parity.None, 8);
   if (!_serialPort.IsOpen)
  {
     _serialPort.Open();
  }
  _serialPort.DataReceived += new SerialDataReceivedEventHandler(_serialPort_DataReceived);

  txtQty.Text  = _serialPort.ReadExisting();
  if (_serialPort.IsOpen)
     {
        _serialPort.Close();
     }

This code working fine when I check with Break point. but not working in exe. Sometime getting this " Access to the port 'COM2' is denied"

How to resolve this ?

Posted 15-Jun-12 19:18pm

palraj001

Updated 24-Mar-17 19:50pm

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Comments

Sergey Alexandrovich Kryukov 16-Jun-12 1:37am

What is "working in exe". There is no such thing as "working without exe". Do you mean running under VS IDE debugger vs standalong?
--SA

AmitGajjar 16-Jun-12 2:08am

SA, i think palraj have problem with release version of this code. as he mention that, "working fine with beakpoint" it is working fine in Visual Studio. i can see only one problem is access problem from Firewall. he need to add 9600 in firewall allow list.

OriginalGriff 16-Jun-12 3:25am

You do realize that "9600" in the Serialport constructor is the Baud rate, not a port number? And that is has nothing at all to do with firewalls?

AmitGajjar 18-Jun-12 0:13am

Opps.... sorry...

OriginalGriff 18-Jun-12 3:23am

:laugh:
Everyone makes mistakes!

palraj001 16-Jun-12 2:20am

Yes. when I debug the code it is working.

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OriginalGriff · Answer 1 · 2012-06-15T21:31:00

The chance are that it is working in the debugger, because your breakpoint allows enough time for the serial port to actually receive some information.

Serial ports are physical communications devices - data transfer does not happen instantly. In your case, the transfer happens at a rate of 9600 bits per second, which works out at around 960 characters per second. You cannot just open the port, set a handler, read data and close the handler, because in the real world there may or may not be data available, and if a character arrives at the receiver at the wrong time, the receive event handler will be triggered and may get executed after the port is closed by your code sample. This could cause the problem you are describing.

Use the handler event to read the data.
And if you are going to add a handler every time you open the port, you need to remove the handler every time you close it!